Backlight sources of display devices are generally white light backlight sources. The white light emitted by a white light backlight source enters a color filter substrate through a liquid crystal layer, and then exits from a color filter layer of the color filter substrate. Due to the light filtering effect of the color filter layer, a red filter layer filters out non-red light in the white light in a region corresponding to the red sub-pixels, a green filter layer filters out non-green light in the white light in a region corresponding to the green sub-pixels, and a blue filter layer filters out non-blue light in the white light in a region corresponding to the blue sub-pixels. That is, a significant part of the white light emitted by the backlight sources will be filtered by the color filter layer, causing a color gamut of the light finally emitted by the display device to be smaller than that of the original light emitted by the backlight sources.